What is an M?

[Allyssa]

My cousin had planned to go to the US (from Canada)for a volunteer program. She had contacted the US embassy and was told only that it might be helpful for the coordinators of the program she is joining to send a letter describing the program. She arranged that. She asked about needing a visa and they clearly said no. Yesterday she went to leave the country and was stopped by "homeland security" and told that she "needed an M" (and were exceedingly rude in the process!). She asked if this was a type of visa or what exactly it was and the staff there simply laughed and called it "an M". She ended up staying here and will try to get this arranged. Has anyone else has a similar experience? Does anyone know what an M is? How long it takes to get one arranged? or the people to contact regarding this?

[Reba]

I believe there is a specific visa for volunteers in the US. Its classed under the same as religious missionaries I think. I really don't know anything about it though, do a search on the USCIS website through the forms maybe? http://www.uscis.gov/portal/site/uscis